As rolling bearings built into automotive electrical parts and accessories such as a fan coupling device, an alternator, an idler pulley, an electromagnetic clutch for a car air-conditioner, and an electric fan motor, ball bearings such as a deep groove ball bearing and an angular contact ball bearing are widely used in order to rotatably support, to a stationary member, a rotation shaft which is rotationally driven by output of an engine.
In general, as illustrated in FIG. 11, a ball bearing includes an inner race 1, an outer race 2, balls 3 interposed between the inner race 1 and the outer race 2, and a retainer 4 for retaining the balls 3. Further, as the retainer, a resin crown-shaped retainer is sometimes used. The resin crown-shaped retainer 4 is made of a resin excellent in abrasion resistance, seizure resistance, and the like. As illustrated in FIG. 12, the resin crown-shaped retainer 4 includes a retainer body 5 having an annular shape and including: recesses 7 formed in one axial end surface 6 of the two axial end surfaces 6 and 10 of the retainer body 5 along a peripheral direction at predetermined pitches; and a pair of claw portions 8, 8 provided to protrude from opening ends of each of the recesses 7, the opening ends being opposed to each other in the peripheral direction. Each of the recesses 7 and the pair of claw portions 8, 8 form a pocket 9 in which each of the balls 3 is received.
By the way, the rolling bearing is required to achieve reduction in torque. Various bearings specified for reduction in torque have been proposed (Patent Literatures 1 and 2). Patent Literatures 1 and 2 disclose the following retainer. Specifically, the retainer is formed in such a manner that a pair of pressed plates is fastened together by fastening means. Recesses for a pocket are formed in an inner surface of each of the pressed plates, and the opposing recesses for a pocket form pockets in which balls as rolling elements are fitted. Further, in an inner surface of each of the recesses fora pocket, a recess or the like is formed as a lubricant (grease) reservoir.